Various kinds of rubbery polymers have synthetically been produced. Among these polymers the plastomers or thermoplastic elastomers are of particular interest. These thermoplastic elastomers are synthetic rubbers of block copolymer structure having terminal blocks of various nearby molecules to establish resinous domains that serve as junctions in a network otherwise containing rubbery blocks. The resinous domain junctions or physical crosslinks form automatically upon synthesis of the block copolymer. The rubber thus produced exhibits substantial tensile strength in the absence of a chemical curing process. The domains of the end blocks just mentioned soften upon heating so that it is possible to form this rubber into the desired shapes by way of techniques known for the forming of thermoplastic articles.
The utilitarian values of these thermoplastic elastomers are inherently restricted by their susceptibility to attack by substances such as oil and ozone. The thermoplastic elastomers when fabricated into articles such as hoses, gaskets, motor mounts, and the like, are subject to weakening and dimensional distortion when they are contacted with fuels and lubricants during their use in automotive and aircraft applications, for instance.